ATLAS-5194: Add pagination while fetching relationships of an entity

[sheetalshah1007]

What changes were proposed in this pull request?

Introduces searchRelatedEntitiesV2 with graph-layer pagination support, achieving a significant performance improvement for large datasets and deep pagination scenarios (offset > 1000). The new method selects between database-level pagination (for unsorted queries) and traditional Gremlin traversal (for sorted queries), while maintaining full backward compatibility with the existing searchRelatedEntities method

Why It Was Needed?

The earlier searchRelatedEntities implementation applies default sorting by the name attribute in ascending order when no sort criteria are provided. This requires loading all related entities into memory before sorting and pagination can be applied. As a result, queries involving a large number of relationships or high offset values suffer from significant performance degradation, leading to long response times and, in some cases, timeouts.

How was this patch tested?

Performance validation was conducted on test databases with 100, 1K, 10K, and 50K entities(relationships), measuring server-side execution time from audit logs across multiple manual test scenarios.

Performance Impact (Accurate Data)

Scenario	Dataset	Offset	Original	V2	Speedup
Medium	10K	5,000	681 ms	55 ms	12.4x
Deep	50K	25,000	3,185 ms	136 ms	23.4x ✅
Extreme	50K	100,000	3,371 ms	122 ms	27.6x

• No regression for sorted queries